1. Field of the Invention
The present invention relates to cosmetic and/or dermatological compositions useful for preventing and/or combating skin blemishes and/or for combating the ageing of the skin. The present composition may be provided in the form of a smooth white cream which may be applied to the human face, body and/or legs and more especially to the hands. The present invention also relates to the dermatological treatment of the skin and to a method of combating skin blemishes and the ageing of the skin by applying such a composition to the skin.
2. Discussion of the Background
During the ageing process, various signs which are very characteristic of this ageing appear on the skin, reflected especially in a modification of the cutaneous structure and functions. This ageing is physiological in nature but may also be photo-induced, that is to say due to a repeated exposure of the skin to sunlight, especially ultraviolet light. The action of this light on the constituents of the skin and on the sebum secreted by the skin results, in particular, in the formation of oxygenated free radicals. These radicals cause considerable damage, especially in cell membranes (permeability of the membranes), in cell nuclei (mutation by action on RNA or DNA) and on tissues (necrosis and degeneration); it is thus necessary to protect the skin from these free radicals.
The main clinical signs of cutaneous ageing are especially the appearance of deep wrinkles and fine lines, which increase with age. In particular, disruption of the "grain" of the skin is observed, that is to say that the microrelief is less uniform and is anisotropic in nature.
Moreover, the skin complexion is generally modified; it appears paler and yellower, which seems to be due essentially to disruption of the microcirculation (less haemoglobin in the dermal capillaries). Furthermore, many colored and/or darker blemishes appear on the skin surface, and more especially on the hands, imparting heterogeneity to the skin. In general, these blemishes are due to considerable production of melanin in the skin epidermis and/or dermis. In some cases, these blemishes may become cancerous. Thus, it is increasingly sought to reduce these blemishes, or even to eliminate them. Moreover, diffuse irritations, and sometimes telangiectasia, may occur in certain areas of the skin.
Another clinical sign of ageing is the dry and rough appearance of the skin, which is essentially due to a more considerable desquamation; by diffracting light rays, these squama also contribute towards the somewhat grey appearance of the complexion.
Finally, a loss of firmness and of tonicity of the skin are observed which, as in the case of wrinkles and fine lines, is at least partly explained by a dermal and epidermal atrophy and flattening out of the dermoepidermal formation; the skin is thinner and more flaccid, and the thickness of the epidermis decreases.
It is thus observed that the clinical signs of cutaneous ageing result essentially from a dysfunction of the main biological mechanisms occurring in the skin.
It is known, from document JO2-200,622, to combine kojic acid with a compound chosen from derivatives of para-aminobenzoic acid, salicylic acid or methoxycinnamic acid and benzophenone derivatives in order to prevent the skin pigmentation and erythema induced by ultraviolet rays.
Moreover, a bleaching composition containing a flavonoid, kojic acid, butylmethoxydibenzoylmethane and methoxycinnamate, which act as ultraviolet screening agents, is known from document FR-A-2,680,466. Butylmethoxydibenzoylmethane has the drawback of being photo-labile (that is to say of being destabilized in the presence of light, which is particularly inconvenient for a screening agent). Thus, in order to enhance its stability, it is necessary to combine it with another screening agent of cinnamate type, thereby complicating the manufacture of the composition.
In addition, many compositions intended to combat the signs of ageing exist on the market. Unfortunately, the effectiveness of these known compositions is often still insufficient.
Thus, there remains a need for compositions which are more effective than those of the state of the art for preventing and/or combating the ageing of the skin and/or skin blemishes.